1. Technical Field
This invention generally relates to semitrailer landing gear and, more particularly, to a landing gear assembly that can be mounted in an inboard or outboard configuration. Specifically, the present invention relates to a single reduction landing gear assembly including a housing having an outer perimeter that fits within the standard mounting bracket for a tractor trailer thus enabling an inboard or outboard mounting configuration. The landing gear also has an improved gear assembly.
2. Background Information
Tractor trailers are a predominant means of transporting goods throughout the world. Trailers are popular because goods do not have to be loaded and reloaded as trailers can deliver directly to the cargo bay of the destination. Trailers also can be detached from a tractor and pulled by another tractor allowing goods to be transported in a trailer without driver downtime. A driver thus can drop off a loaded trailer for unloading and pick up a loaded trailer that is ready to ship.
Trailer landing gear supports the front of a trailer when the trailer is detached from a tractor. Trailer landing gear typically includes a pair of laterally-spaced, gear-driven telescopic legs mounted on the front end of the semitrailer. The gear boxes of each leg are linked by a shaft allowing a single crank to be used to raise or lower both legs simultaneously.
The following description of the use of two-speed landing gear is provided as general background information. A typical scenario begins with the operator of a truck tractor dropping off the semitrailer at a location such as a dock for loading or unloading of the semitrailer. This semitrailer is retrieved when loading or unloading is completed, often by another tractor. When disconnecting after positioning the semitrailer in the desired location, the truck operator manually turns a crank handle to extend the legs of the landing gear until the legs engage the ground. The operator typically uses the high gear or high speed of the two-speed gear assembly to quickly extend the landing gear legs from the retracted position to the extended position where the legs contact the ground. It should be noted that when the landing gear assembly is engaged in high gear, quick traversal of a vertical distance is accomplished due to the low ratio of crank handle turns to inches of vertical leg travel distance afforded by the high gear, which ratio usually is from about 2 to about 5 depending on the unit being utilized. The tradeoff for such a low ratio achieved in high gear is a lower mechanical advantage than the mechanical advantage that can be achieved in a lower gear. In practical terms, this means that the truck operator cannot raise or lower a load in high gear. In low gear the ratio of crank handle turns to distance traveled is higher, usually from about 15 to about 50, but a higher mechanical advantage is enjoyed. The high mechanical advantage enables the truck operator to raise or lower loads in low gear that could not be moved in high gear, albeit at a slower pace than if such loads could be moved in high gear. In order to pull the truck tractor away from the stationary semitrailer, the operator must disengage the depending kingpin of the semitrailer from the fifth wheel of the truck tractor by disengaging the fifth wheel jaws. Since the tractor is spring-biased in an upward direction, it is desirable to raise the semitrailer to relieve some of the load allowing the tractor to pull away from the semitrailer more easily. The operator may therefore shift the gear assembly to low gear in order to further extend the landing gear legs and raise all or part of the load of the semitrailer from the fifth wheel. After releasing the movable jaws of the fifth wheel, the tractor is disengaged from the semitrailer.
When an operator picks up a semitrailer that has been loaded or unloaded, he must back the truck tractor fifth wheel under the semitrailer and engage the kingpin. If the semitrailer was resting on a stable surface such as concrete, and a similar tractor is utilized, the necessary clearance to allow coupling most likely still exists between the ground and the kingpin, and the operator merely will back the truck tractor under the semitrailer engaging the kingpin. The operator will shift the landing gear into low gear to lower the load onto the tractor, then shift into high gear and quickly retract the legs to provide clearance for vehicle operation. More particularly, the legs are positioned approximately one foot off of the ground to provide clearance for over-the-road travel. However, if the semitrailer was left on a relatively unstable surface such as soft ground or blacktop, the semitrailer legs sometimes sink into the ground under the load of the trailer between the drop off and pickup times. If this is the case, or if a higher tractor is employed, the operator must further extend the legs to raise the trailer to provide sufficient clearance between the ground and the kingpin. This requires the operator to shift the landing gear into low gear to gain mechanical advantage to raise the trailer. After coupling to the tractor and lowering the trailer load onto the tractor using low gear, the operator then will proceed as descried above to retract the legs in high gear to position the legs for over-the-road travel. This process is common to essentially all types of landing gears.
Landing gear legs are mounted in both inboard and outboard configurations. The choice of mounting arrangement depends on the type of trailer, the type of landing gear, and the manufacturer. One of the problems with existing semitrailer landing gear is that the gear box or gear housing located at the top of the telescoping legs prevents one side of the landing gear from being mounted on the trailer frame. The protruding gear box thus provides only one available mounting surface on the landing gear. Such landing gear can only be mounted on one side of the frame member of the trailer thus requiring the landing gear manufacturer to provide both inboard and outboard configurations. Trailer manufacturers thus desire a landing gear that may be mounted in the inboard or outboard configuration.
Another problem with existing gear box assemblies is that the shaft location of the gear box assemblies does not allow the landing gears to be switched between inboard and outboard mounting. Landing gears are mounted with a standard hole pattern having a pentagon-shaped central opening surrounded by a plurality of bolt holes. Existing outboard landing gears are designed to position the inner connecting shaft within the central opening. Inboard landing gear positions the input crank shaft within this opening so that the crank can be easily accessed by the user at the outside of the trailer. The art desires a landing gear assembly that locates the crank shaft in a manner that allows the crank shaft side of the landing gear to be mounted on the inboard side of the trailer frame.
Another problem in the art is that the gear assembly used to raise and lower the legs of the landing gear must be able to be easily assembled. Assembling the gear assembly inside the legs of the landing gear can be especially difficult given the limited volume within which to work. The art thus desires any gear assembly for a landing gear to be able to be assembled without extraordinary efforts. The art also desires that the gear assembly does not take away from the strength of the legs of the landing gear. It is desired to provide a gear assembly that strengthens the landing gear.